There is an increased demand for clean and renewable energy sources to negate the adverse effects of utilizing hydrocarbon fuels and the release of carbon into the atmosphere. Hydrogen production is one such proposed solution as it is a clean fuel, producing only water when consumed.
However, currently the majority of hydrogen, approximately 90%, is industrially produced from the gasification of fossil fuels such as natural gas, oil and coal. However, these processes still lead to the emission of carbon dioxides. Therefore, as hydrogen is not generally obtained from carbon oxide free sources, it is not carbon neutral energy source.
Accordingly, there is a growing and renewed interest and need for the production of hydrogen through the electrolysis of water. The production of hydrogen through the electrolysis of water using diaphragm cells is well known. The use of diaphragm cells for the commercial production of hydrogen and oxygen, such as the Knowles and Stuart cells is well established. However, the disadvantage of these conventional diaphragm cells resides in the production of low energy efficiency and low capacity, with approximately 65% energy efficiency in the Knowles cell and approximately 55% in a Stuart cell.
FIG. 1 illustrates a conventional diaphragm cell in water electrolysis where the standard electrode potential E°=1.229 volts and the electrolyte is the same in both the anode cell and cathode cell. However, the diaphragm in such conventional cells remains particularly problematic, wherein it increases impedance and agitation of the electrolyte to reduce over-voltage becomes difficult. The diaphragm must enable electrons to pass through with minimal resistance but must prevent mixing of oxygen and hydrogen produced at the anode and cathode respectively.
In U.S. Pat. No. 7,326,329 and related United Kingdom Patent GB2409865 and Australian Patent 2004237840 titled “Commercial Production of Hydrogen from Water”, there is proposed a process for the production of hydrogen from the unipolar electrolysis of water, wherein more hydrogen is produced from the same energy to produce 1 mol of hydrogen from the electrolysis of water.
U.S. Pat. No. 6,475,653 titled “Non-diffusion Fuel Cell and a Process of Using a Fuel Cell” attempts to address the recognized problematic issues with the diaphragm in electrolytic cells, wherein there is disclosed a more efficient hydrogen fuel cell that operates without a diaphragm or membrane. This allows clean electrical energy and transport energy to be derived from renewable energy such as solar and wind.
Accordingly, it is an object of the present invention to provide an improved diaphragm electrolytic cell and an improved process of production of hydrogen from the electrolysis of water.
The present invention provides higher rate of hydrogen production from the electrolysis of water using the structure of the conventional diaphragm type electrolytic cell, wherein a diaphragm is positioned between the anode and cathode or an electrolytic membrane or a salt bridge or semi-conductor or conductor between the anode and cathode. However, instead of utilizing the same electrolyte in both the anode cell and cathode cell, as that disclosed in U.S. Pat. No. 7,326,329, an acid electrolyte is passed through the cathode cell while an alkaline electrolyte is passed through the anode cell. Utilizing the Latimer equations, the standard electrode potential E° becomes −0.401 volts, compared to that of the conventional diaphragm cell where the standard electrode potential E°=1.229 volts to produce hydrogen and oxygen from the electrolysis of water.
Notably, the efficiency of the electrolytic cell of the present invention is improved as only one of the electrodes of the cell is connected to the power supply. Advantageously, this eliminates any unwanted side reactions at the cathode and anode such as the production of oxygen and hydrogen respectively. Therefore, the efficiency of the electrolytic cell is improved.
A further advantage of the present invention resides in the utilization of the acidic and alkaline electrolytes of the cell to produce hydrogen and oxygen. The acid electrolyte exiting the cathode cell, which contains an excess of OH− ions that makes the acid electrolyte negative in electrical charge. Additionally, the alkaline electrolyte exiting the anode cell contains an excess of H+ ions that makes the alkaline electrolyte electrically positive. These two electrolytes are passed through another set of electrolytic cells with a diaphragm type structure, wherein the electrolytes will tend to neutralize each other resulting in a current flow. According to Faraday's Law, this will result the production of hydrogen and oxygen.
Other objects and advantages of the present invention will become apparent from the following description, taking in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed.